Dental cements are used for adhering dental restoratives such as crowns, bridges, inlays and onlays to a tooth, providing a lining in a tooth cavity, fixing orthodontic appliances to the teeth and sealing root canals after endodontic treatment.
The dental profession has traditionally used durable cements for permanent restorations and temporary cements for temporary or provisional restorations. A durable cement is used for permanent restorations and is required to last for at least one year. A temporary cement can be used for up to three months as temporary or up to one year as provisional.
The commonly used dental cements for long term restorations are zinc phosphate cement, zinc poly(carboxylate) cement, glass ionomer cement and composite cement. These cements have good adhesion characteristics yet also exhibit high brittleness. The temporary dental cements are required to retain a temporary or provisional restoration for a specific period of time, but then allow the dentist to remove the restoration without having to apply undue pressure to the tooth or restoration. They are most commonly used for the period between the preparation and seating of a permanent restoration to ensure that the prepared tooth (teeth) is (are) healthy prior to permanent restoration. The traditional dental cement for temporary restorations is zinc oxide-eugenol cement, which has been used for over 100 years.
The zinc oxide-eugenol cements have demonstrated good biocompatibility, excellent sealing characteristics and effective bactericidal characteristics. They have found wide application in dentistry. Unfortunately, these materials have poor optical characteristics, being very opaque in appearance. These materials also inhibit free radical polymerization because of the presence of an electron-rich phenolic hydroxyl group in the eugenol molecule. Thus, acrylic resins, and to a lesser extent composites, in contact with a zinc oxide-eugenol cement do not polymerize completely. This incomplete cure results in polymer surface regions having reduced physical properties such as low surface hardness. Furthermore, zinc oxide-eugenol cements have a penetrating, long-lasting odor and lingering taste that can be unpleasant to many patients. In addition, incompletely hardened cements containing residual eugenol may produce irritation and cytotoxicity.
Crisp et al. in U.S. Pat. No. 4,016,124 disclose cements comprising acrylic acid/itaconic acid copolymers and fluoroaluminosilicate glass powder. Brauer et al. in U.S. Pat. No. 4,362,510 disclose cementitious dental compositions comprising a solid phase which includes a metal oxide or hydroxide of tin or a Group II metal and a liquid phase that includes a vanillic acid ester chelating compound. Brauer et al. in U.S. Pat. No. 4,486,179 disclose biocompatible cementitious dental compositions containing a syringic acid ester. Akahane et al. in U.S. Pat. No. 4,591,384 disclose a dental cement composition containing a water-soluble tannic acid derivative. Futami et al. in U.S. Pat. No. 4,773,933 disclose putty-form dental zinc oxide eugenol cement compositions. Billington et al. in U.S. Pat. No. 4,797,431 disclose radiopaque glass/poly(carboxylic acid) cement compositions. Engelbrecht in U.S. Pat. No. 4,872,936 discloses polymerizable cement mixtures containing acid monomers and reactive fillers. Mitra in U.S. Pat. No. 5,130,347 discloses a dental cement system containing a photocurable ionomer, reactive powder and water that undergoes both a self-curing reaction and a photo-curing reaction. Combe et al. in U.S. Pat. No. 5,141,560 disclose a dental cement comprising calcium or zinc oxide or hydroxide, a substituted aromatic compound and dry poly(carboxylic acid). Cohen et al. in U.S. Pat. No. 5,154,613 disclose dental cements for a temporary dental prosthesis or appliance containing a metal oxide, a metal hydroxide and an aqueous solution of a polycarboxylic acid. Lu et al. in U.S. Pat. No. 5,338,773 disclose further dental cement compositions and a method of use. These cement compositions include polymerizable acid reactive ethylenically unsaturated monomers, and a source of cations reactive therewith, to further crosslink the resulting polymer. Huang et al. in U.S. Pat. No. 5,367,002 disclose dental compositions formed by mixing a curable liquid composition containing polyalkenoic acid with a powder containing reactive fillers. Voigt et al. in U.S. Pat. No. 5,403,885 disclose a transparent dental bite-registration material based on addition-crosslinking polysiloxanes. Mitra et al. in U.S. Pat. No. 5,453,456 disclose a glass ionomer cement containing a silane-treated fluoroaluminosilicate glass. Huver et al. in U.S. Pat. No. 5,700,891 disclose a low-odor adhesive composition comprising (meth)acrylates containing urethane groups. Rheinberger et al. in European Patent No. 0 475 239 disclose dental compositions containing ethylenically unsaturated monomers and filler with a silica-metal oxide mixture and quartz or glass powder.
The prior art zinc phosphate cement, zinc poly(carboxylate) cement, glass ionomer cement and composite cement are strong, brittle and only suitable as permanent cements. There is no indication that these cements would be considered useful for temporary cementations because removal of the temporary prosthesis or appliance from the dental tissue is very difficult. The prior art zinc oxide-eugenol cements are very opaque, and alter the inherent, slightly translucent shade of temporary restorations. Furthermore, the prior art temporary cements are difficult to clean from both the temporary prosthesis or appliance and the dental tissue.
Problems typically arise after placing and curing in the tooth an opaque temporary cement for the cementing of temporary restorations such as inlays, onlays, crowns and bridges made of relatively transparent materials, e.g., porcelain or synthetic resin composites. The shade of the temporary is greatly affected by showing-through of the opaque temporary cement.
Accordingly, it would be desirable to provide an improved cement composition that is highly translucent, elastomeric and suitable for temporary or provisional restorations. It would also be desirable to provide a cement that retains a temporary or provisional restoration for a specific time period, then permits a dentist to easily remove the restoration. It would further be desirable to provide a cement that cleans up easily after it has set, and is easily removed from the temporary or provisional restoration and easily removed from the tooth tissue.